A 7-day continuous intravenous infusion of cytosine arabinoside plus a 3-day schedule of intermittent daily doses of Adriamycin has been shown to be as effective chemotherapy for the induction of remission in adults with acute nonlymphocytic leukemia as the combination of cytosine arabinoside with daunorubicin. A complete remission rate of 65% has been obtained with either combination. However, the adriamycin combination has been shown to be more toxic and to require more careful dosage adjustment and monitoring of blood levels. The addition of either neuraminadase-treated allogeneic myeloblasts or splenectomy to chemotherapy during remission maintenance treatment enhances the duration of remission and survival of patients. Reverse transcriptase has been identified in the bone marrow cells of leukemia patients prior to treatment and in morphologically normal peripheral cells during complete remission. The leukemic cells of patients with acute progranulocytic leukemia have been shown to differentiate in vitro with cis-retenoic acid. Treatment of those patients with cis-retenoic acid has not produced differentiation in vivo, however,